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Post by detonatortuning on Apr 18, 2011 19:10:12 GMT -5
Hi fella's, after alot of hesitation over starting a new thread on this i've gone ahead so that i can keep the info shared and replied in context to my situation.
a co-worker has a triton that at 7,000 mls. lunched the wrist pin bearing and siezed the engine at walking speed just before an intended stop. the engine never restarted before i took it down to find the reason for the stall.
while putting a 90cc from scrappy in it for him i inherited this stock engine. i was thinking to use another 90cc in a project of my own but have begun to seriously consider re-deploying this engine instead.
it has been put forward that this stock 50cc longcase could be restored with a simple topend replacement, which is resonable to me, but i'd like opinions of the likely longevity of this engine with a new topend and a 7,000 ml. stock crank that was subjected to a hard failure seize ?
now what i'm after is to put this engine in an 81# fully enclosed tadpole trike streamliner with a .2 CD to use as a commuter on a 30 ml. round trip daily work run.
the very best spreadsheet i can find suggests that it will take 2.9HP to push this thing with my weight in it 50 MPH constant. the triton is rated at roughly 4.9HP @ 7,000rpm unrestricted ( perhaps optimistically, i don't know. that's just what i found online ). the biggest question is does this engine have the gearing and torque needed to move this vehicle 50MPH at the rpm it's putting out roughly 3HP ?
if not i'll consider putting an iron 70cc kit on and some gears in it, but i'd be back to having serious questions about the stock crank and bearings.
this isn't my first 2 stroke experience but these are my first small bore, CVt scooter style driveline projects so any and all replies and opinions are gratefully appreciated.
thanks, steve
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Post by 90GTVert on Apr 18, 2011 19:28:16 GMT -5
The Triton should have sufficient gearing to be able to do 50. I've done as much as 70MPH with stock gears on one of mine, that was at 11,000RPM with a lot more than stock power though.
Power would be my primary concern. If it were a scoot, I'd say no way. Not a good idea to get it and think you'll be cruising at 50. In a little streamliner, I'm not honestly sure what to think. Aerodynamics is definitely a big part of the game even at 50MPH with the horsepower we're dealing with. I would guess they probably do make somewhere around 4HP unrestricted. I dunno. Never had access to a dyno to really know HP figures. It'll at least do that 2.9HP. Headwinds and hills and all that might be a setback if you are right on that mark though.
As for the crank, with those circumstances I would replace the crank and bearings. I know some scoots go a lot longer than 7,000 miles on a stock bottom end, but it just seems safer to replace that stuff. If you can't replace it at least check it all over for play and smooth movement.
If you do the project, pics would be cool. Sounds neat.
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Post by detonatortuning on Apr 18, 2011 19:56:10 GMT -5
thanks Brent,
the project is IN, even at 50mpg in my geo metro xfi i can't or maybe just won't do $40.00 fill ups that only last 2 weeks.
i have a trek mountain bike with a 46cc GP460 ( 4.2HP / 2.2 #'s ft. ) go-ped engine on it that does 50+mph at 120mpg. the CD is about .9 with me in riding position.
i'm seriously looking at this streamliner doing 200+mpg i just need to set up a very efficient engine for it.
for background look at blueskydsn.com, electrathon / aerocoupe.
steve
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Post by 2strokd on Apr 19, 2011 8:38:05 GMT -5
In a nutshell ide say 50MPH with good mileage is possible on a stock scoot with minor mods. A far as wind or hills go, forget holding that speed. I think a good sport kit would be a good idea! Even a 50cc one! Whos tried that? I bet you would get the good grunt and enough up top to hold you at around 50 over minor hills and wind. And still get good MPG... Shoot, now im thinking about aftermarket 50cc kits! LOL
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Post by 90GTVert on Apr 19, 2011 10:06:24 GMT -5
I think I'd go with a 70cc sport kit that's built for low end, like the Polini for example. Reason being, they require less throttle to accelerate and maintain speed. Keep a stock or street style pipe (I love the Phongeer I have on the Venus) so you improve that torque rather than losing it like you will with anything beyond the street pipes. Depending how it turns out, maybe even try for slightly deeper gears than stock. From my experiences so far the added torque and gearing to allow me to hardly touch the throttle to accelerate has added up to greatly improved mileage. Nothing I've done is near your 100 and a far cry from 200, but by doing those things to one scoot it gets 30MPG more than any other similar displacement scoot I have. The problem here being that if you spend a bunch of money on a cylinder kit (of any displacement) and pipe and gears etc... you are negating some of your savings so it's gonna take a long time for it to pay off.
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Post by detonatortuning on Apr 19, 2011 12:08:55 GMT -5
thanks guys, good points. and kind of support some things i'd been thinking.
WILL need atleast 70cc of good low / mid range as suggested, WILL need new crank, bearings, seals etc, etc.
WILL need gears, based on thread i found where Brent says that it takes 9700rpm to get 50mph out of the stock vento gears. i don't want to be ringing it's neck to do 50, i want that to be a steady mid to upper mid range cruise.
the small weight and profile of this thing is going to make a huge impact on both performance and mileage as viewed from my experience with the go-ped / bike. even with just 2.2 #'sft. of torque at 9,000rpm it takes wind i don't want to ride in to slow it down. i formerly had it geared to do 50mph at 9,000rpm it was ok, only slowed slightly on hills and wind. now i have it geared to do 50mph at the 11,000rpm power peak ( it will turn 13,000 rider up )and it doesn't slow down at all.
bottom line of an engine built to do this on small bores, even 70cc, is that money wise i might as well just get another 90cc, and let it do the job totally relaxed. the one i replaced this engine with is pushing a 250# guy very close to 60mph on a 207# triton R4 and is getting faster the more it's run.
thanks for all the great feedback, sorry i tend to think thru my hands at times : )
steve
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Post by 90GTVert on Apr 19, 2011 13:41:32 GMT -5
One thing that gets confusing is trying to figure out the actual RPM needed to get X speed when dealing with a CVT transmission. I'll give you an example...
My Keeway Venus (96cc, built for torque) - 11.08:1 Final Drive Ratio - 53.2" Tire Circumference
If you take those figures and punch them in for 9,000RPM, that scooter should do 41.2MPH.
My Vento Triton 103cc - 11.125:1 Final Drive Ratio - 58.5" Tire Circumference
If you plug those figures in for 9,000 RPM, that scooter should do 45.2MPH.
The Triton's numbers are actually pretty close, but the Venus has gone 61MPH at 9,000RPM. So why are the numbers so far off? You're calculating with clutch bell RPM instead of engine RPM when you use the calculators I have up. Because of the low end power that the Venus makes, I can use very heavy (9.5g) sliders so that the engine spins slower to get the rear pulley going faster. Whereas the Triton is using 7.5g sliders to keep revs up.
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Post by detonatortuning on Apr 20, 2011 7:58:55 GMT -5
In a nutshell ide say 50MPH with good mileage is possible on a stock scoot with minor mods. A far as wind or hills go, forget holding that speed. I think a good sport kit would be a good idea! Even a 50cc one! Whos tried that? I bet you would get the good grunt and enough up top to hold you at around 50 over minor hills and wind. And still get good MPG... Shoot, now im thinking about aftermarket 50cc kits! LOL i see from Brent's 90cc project thread that you guys are actually going after this option. i will be VERY interested in how that turns out ,please keep me in the loop on discoveries and outcomes. i CAN do either but i'd rather do this just once with the smallest engine ( what ever that turns out to be ) and best mpg's possible. thanks, steve
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Post by detonatortuning on Apr 21, 2011 13:36:24 GMT -5
several new encouraging points, found out about 50cc sport topends and fullcircle cranks.
also stumbled into an idea in Brent's project 90 thread of converting the out put to sprocket drive and having virtually infinite final drive options over the top of the scooter cvt.
the sprocket idea could be the answer i've been waiting for to get 50mph out of roughly 5HP at the design powerpeak of the 50cc engine.
as always, thanks for any pointers or opinions steve
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Post by detonatortuning on Apr 24, 2011 20:23:40 GMT -5
yet another idea on the forward engine and sprocket out put has surfaced over in another thread and i'll comment on it here where it applies to my circumstances rather than fill up that thread with it.
the Derbi GP1 50 Racing has the engine moved forward under the footboards, a full mono shock swingarm and rear disk brake. pretty cool stuff.
i found an online place where you can buy the whole scooter piece by piece. ok, but priced out of the question. the swingarm and bare rear wheel are each over $750. each not to mention the brake parts, bushings ect, ect. just the 2 main parts together would double the cost o fmy project.
i can still pursue the sprocket output by using a 16" Tomos moped rear mag. they are designed for the sprocket to be on the left on the Tomos but nothing in the drive hub or brakes would prevent it from being fliped and driven from the right.
i will still have the room for a swingarm just need to work one up and establish upper shock mount(s) as needed.
more later, steve
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Post by reveeen on Apr 25, 2011 19:35:15 GMT -5
If it was me, I would consider a 4 stroke over a 2 stroke, if mileage was my goal.
For a remote rear wheel/swing arm take a look at pit bike components (EBay).
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Post by 90GTVert on Apr 25, 2011 20:53:19 GMT -5
Yeah, I love those pitbike motors. Of course the 4T can be more fuel efficient. Never checked mileage on any of them when I rode the little bikes. They are already setup for 420 chain with a few different front sprockets available. Lots of different rear sprockets for that chain size could be adapted. I mounted one of those engine on a kart, so I know there are sprockets that are meant for wheels and to be axle mounted. Available in many sizes. Full auto, semi-auto, manual trans. All sorts of options, much more affordable than what you've been looking at with the Derbi. Good idea reveen.
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Post by reveeen on Apr 27, 2011 6:32:14 GMT -5
I have a Jawa/Chinese pit bike hybrid 140cc moped here that works ok. The little pit bike wheels take scooter tires (with tubes), and offer disk brakes (front and rear). 60mph and all the wheelies I can stand.
No idea on the mileage, not a factor in my case, but a fellow should go out and look at a pit bike (to see if it "fits" with his ideas)?
I have seen them used from $100. I bought my donor new (in the crate) for $500 delivered to my door.
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Post by 90GTVert on Apr 27, 2011 6:43:27 GMT -5
You should be able to get 110-125cc engines for around $300 new. Those would be capable of 50MPH pretty reliably in detonator's app I believe if it were a semi-auto or manual. I've dealt with all of them and the power improves as your effort increases. Full auto = least powerful. Semi-auto (you shift, auto clutch) = a little more powerful. Manual = Noticeably more powerful.
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Post by detonatortuning on Apr 27, 2011 11:35:53 GMT -5
these all good and apprec'd points.
i am aware of and had looked at that market quite alot. there are preferred design requirements that had favored cvt scooter power.
primarily the fact that if i could do it ( and i'm still convinced i can ) on 50cc 2t, MY state will still recognize it as a scooter, and i have all the associated benefits. if i go with a 4t of the capacity nec. to give me the power i need i forfit those benefits. and am forced into the "specialized construction" class which i CAN do but prefer for obvious reasons not to.
secondarily, e-start greatly simplifies my objectives, although i have already designed a work around if i can't get the engine i want other than kick only.
additionally, elec. cold start enrichment ( choke ) is a real plus due to the streamliner body panels and engine positioning. i haven't exhausted the search for this feature on 4t carbs yet either. and could make a panel to reach thru and deal with it.
furthermore, i HAVE to have enough stator / charging output to run full lighting, hi and low beams, stop, turnsignals. i have extreemly good LED units available to help cut the current draw as much as possible. i have found some vendors that have engines with lighting capabilities, i'll have to check into the actual output.
that leaves the whole shifting issue. this also threatens the scooter class inclusion in MY state. semi -auto would be the best compromise because i could keep the lever inside the opperators cabin and shift by hand. a clutch cable, handle and a remote shift linkage to get it all the way up front to my foot while not impossible would be cumbersome at the least.
if not for the whole lighting issue i would have already installed one of the harbor freight greyhound engines and run it thru a toruqe-a-verter ( go cart, mini bike ) style cvt. the 6.5HP unit is on clearance for $78.00 with coupon.
there are ALOT of things to consider in this project and i thank all of you for the support of ideas and comments so far.
thanks, steve
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